Student makes his own Air Conditioner to beat the summer heat. | Hacker News Reader

Student makes his own Air Conditioner to beat the summer heat.

gmilburn.ca

17 pointskaranbhangui21 comments

Let's calculate quickly: a typical small room might require 5000 Btu/h to cool. One Btu is equal to a 1F temperature rise for 1 pound of water. Assume that "Black Beauty" can get 20 degrees of thermal differential out of the water running through it (incoming: 50F, outgoing: 70F). That means we must pass 250 pounds, or just over 31 gallons, of water through the system each hour.

That wouldn't be so bad if the water could be put to another use, like bathing, watering a vegetable garden or flushing toilets. But, 750 gallons of water a day is A LOT to use just for cooling -- consider that this is equivalent to four times the typical American household usage for a day.

As with a lot of DIY geek hobbies, it's not so awful when one person does it, but it would be an environmental disaster if this was adopted by the general public.

EDIT: Corrected my units.

would be interesting to see something like this combined with a solar hot water heater.

Water is indeed an important resource, but it's not a particularly scarce one in many areas. It's not a waste to use something one is paying for, in those circumstances.

I've lived in areas where water is terribly scarce, and places of plenty, such a I do now. In the places of plenty, some municipalities subsidize the price of water because it's politically popular. Under the guise of helping the poor, they help the middle class that is most of their electorate. Others do not. The ones that subsidize scream about scarcity and waste. That doesn't make it true. Subsidies distort the market.

I don't see your point here. Encouraging waste because a resource doesn't have scarcity seems a bit strange. Perhaps it can be piped to areas that have scarcity? Many rivers etc are dammed to provide municipal water; so oversupply might encourage some muncipalities to un-dam water and let it flow naturally again, which is an env++.

Most importantly, it's good to be in the habit of conserving water, recycling and such because when you move into areas of scarcity, you don't have to force-change your habits and suffer quickly, but instead act responsibly all the way through.

I note your handle is 'capitalist' - being responsible isn't hippy anti-capitalism. Saving a few bucks here and there by using less subsidized water might mean that people will stop expecting subsidy, and instead want the money redirected elsewhere...

and everyone is still richer.

EDIT: i don't disagree that subsidies distort markets, but it's tangental to the parent post.

Usage is not waste. Simply because you don't agree with his usage of a tub of water to cool his room doesn't make it waste. He chooses on what to spend his money. As for the ad-hominem attack on my handle, I'll simply say it's unwarranted.

is it not a waste for someone to open a fire-hydrant so they can bathe their dog's paws? Your definition of "usage is not a waste" is really questionable.

BTW, there was no ad-hom attack on your handle, but rather an observation of your potential leaning -- i'm a capitalist too ( i think most HN'ers are) so I figured i'd respond to make sure you weren't going to write me off as a hippy-enviro.

He doesn't do anything to handle condensation that will form on the cooling coil.

It is called air-conditioning because getting humidity right is just as important as temperature.

That's so true. That is actually why you want to size your AC unit to how large your house is otherwise you will either have the unit running too long and remove all the moisture in the house or have the unit on for only a minute at a time and it won't have the chance to remove any of the moisture. When the latter happens you are cool but it feels like a swamp.

Reminds me when we lost power a few days during a blizzard, and we just ran hot water - supplied by the university, powered by generators - in a bathroom to make a sauna.

Isn't this a tremendous waste of water?

Pretty much. Fashioning your own air conditioning system is a neat way to learn about heat exchangers and condensers and all that, but nothing you make at home is going to be anywhere near as efficient as a modern air conditioning unit.

It's only a waste of water if you assume the water is 'disappearing' afterward. In ontario water is mainly provided by lakes, then after treatment water is returned to the same lakes. The only waste is the power used to move/treat the water, but this is the equivalent of power used by the compressor/fan of a normal A/C anyway.

The situation is obviously different if the water supply is not a closed loop, like in Australia where water is supplied from dams and then waste water in dumped into the ocean...

Actually, I was thinking of my water bill...

No more than conventional air conditioning is a waste of electricity. Use whichever is cheaper, ie less scarce.

I made one of these but used a single cooler with ice cubes+water+frozen saltwater Jars. The system was closed as opposed to wasting water like this guy did.

The big issue was that the water temperature rose very fast and the ice melted way to quickly. You'd get maybe 10 minutes of really cool air and it would be done.

I thought about maybe using hay to keep the ice colder but it was getting to elaborate when the fan would work just fine.

Were you making the ice in a freezer that was in the same room as your "air conditioner"?

I get where you are headed, but you should probably think about the ice as "fuel." The cost (in terms of heat/energy) of freezing the ice can be spent during times when you are not in the room and/or not using the "air conditioner."

Actually there are commercial HVAC systems that use ice as a coolant - the water is frozen at night when electricity demands are lower and then is used to cool the building during the day.

Of course :).

It was in a dorm and I only really ever slept in the bed. SO I would make the ice in my tiny dorm fridge and put it into the A/C's cooler when I wanted to sleep. This happened only two nights.

This is a terrible waste of a very important resource: water. It's amazing to me how many people take it for granted.

In some places there is more than enough water for everyone, so wasting water isn't a concern.

Yes. And if you just have a pump in your garden, and let the water sink in again, after you use it, nothing's being wasted at all.

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